This test measures the total level of the enzyme lactic dehydrogenase, also called LDH, in the blood. LDH is found in many body tissues and organs. Tissue or organ injury can release LDH into the bloodstream, thereby raising the level. The test is usually done to see if tissue or organ damage has occurred.

Who is a candidate for the test?

A doctor may order this test if he or she suspects a heart attack or other tissue damage in the body.

How is the test performed?

In order to measure the amounts of LDH isoenzymes in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a rubber tube is tied around the upper arm to enlarge the veins in the lower arm. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial to be tested in the lab. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.